The invention relates to an x-ray tube comprising two cathode filament coils, one of which, respectively, serving the purpose of generating the x-radiation, comprising a housing comprised of shielding material which surrounds the cathode coils, which housing exhibits an opening for releasing the stream of electrons to the anode.
In the case of x-ray tubes of this type, only one cathode coil, respectively, is employed corresponding to the respectively desired focus. The selective connection (or switching-on) of the respectively employed focus proceeds electrically in the case of the known x-ray tubes. This has as a consequence that, for example, during transition from fluoroscopy to radiography, a relatively great amount of time elapses during the heating up of the respective cathode coil.